Let the average after 7th inning = x

Then average after 16th inning = x - 3

16(x-3)+87 = 17x

x = 87 - 48 = 39

Actual average salary of 12 officers = 400

Total salary of 12 officers = 400 x 12 = 4800

Average of these 12 officers as a whole =60

Total salary of 12 officers as a whole = 60 x 12 = 720

The total salary of rest = 4800 - 720 = 4080

Difference in average of the rest of officers = 60 - 56 = 4

Rest of the officers =

Total number of employees = 1020 + 12 = 1032

A) Rs. 30 | B) Rs. 25 |

C) Rs. 20 | D) can't be determined |

Explanation:

Let the fixed expenditure of the hotel be Rs.x and the variable expenditure ( which is dependent on the guest ) is Rs.y , then

x + 10y = 600 ---------(1)

x + 20y = 800 ----------(2)

10y = 200

y = Rs. 20 and x= 400

Hence the total expenditure when there are 40 guests = 400 + 40 x 20 = 1200

average expenditure = = Rs. 30