1.12.91 is the first Sunday of December 91.
So, 3.12.91 is the first Tuesday of the month.
Clearly, 10.12.91, 17.12.91, 24.12.91 and 31.12.91 are also Tuesdays.
So, 24.12.91 is the fourth Tuesday.

Indian Navy’s survey vessel INS Sarvekshak has become the India’s first warship to install solar power system on board. The solar power system works on sunlight and hence is 100% per cent reliable for power source that can be used for communication equipment, battery charging and general lightings onboard round the clock with battery outputs during night. The system is maintenance free.

Samsung has become the first company in India to launch its mobile payment service named Samsung pay.

India's most consistent middle-order batsman Cheteshwar Pujara stormed his way into record books after playing a marathon innings against Australia on fourth day of the third Test match
surpassing Rahul Dravid previous best of 495 balls. 

Error-first callbacks are used to pass errors and data as well. You have to pass the error as the first parameter, and it has to be checked to see if something went wrong. Additional arguments are used to pass data.

fs.readFile(filePath, function(err, data) {
if (err) {
// handle the error, the return is important here
// so execution stops here
return console.log(err)
}
// use the data object
console.log(data)
})

Let first part is 'K' and second part is 'L'
then K + L = 50000---------eq1
Total profit = profit on x + profit on y
7000 = (K x 10 x 1)/100 + (L x 20 x 1)/100
70000 = K + 2L-----------------------------------eq2
70000 = 50000 + L
so L = 20000 then K = 50000 - 20000 = 30000
first part on 10% is = Rs.30000

Let age of retirement = S
so according to the given condition 25000(x-20)
=10000 x 3 + 12000 + 14000 + 16000 + 18000 + 20000 + 22000 + 24000 + 26000 + 28000 + 30000 + 30000(S-33)
= 30000 + 210000 + 30000S-990000
= 30000S - 750000
or 25000S - 500000 = 30000x - 750000
or 5000x = 250000
or S = 50 yrs.

Railway Minister Suresh Prabhu on 18th March, 2017 flagged off the first fully India-made suburban train 'Medha'. The train will save foreign exchange worth ₹32 crore per rake along with 25% saving in the manufacturing cost. It can run at a maximum speed of 105 km per hour, and has been fitted with LED lights and GPS-based passenger information system.