To find the total cost of machine operation to meet the order, we need to calculate the total number of hours required for the 4 machine working together to meet the order.

Given:
4 machines working simultaneously at a constant rate r to produce of the total order for wrenches.
Remaining wrenches needed as per the order are to be produced in 3 hours with all 4 machines running at the same rate r.
Cost of operating each machine for one hour is Rs 22.00

Now, we can calculate the total number of hours required for the 4 machine working together to meet the order.

Let us assume that total number of wrenches needed as per the order is ‘x’.

Then,
of x =

⇒ 4x =

⇒ x =

Now, as per the given condition,
Remaining wrenches needed as per the order are to be produced in 3 hours

⇒ Remaining wrenches = x –

⇒ Remaining wrenches =

Now,
Total number of wrenches =

⇒ Total number of wrenches = +

⇒ Total number of wrenches =

Now, as the 4 machines are working simultaneously at a constant rate r to produce wrenches per hour,

Total number of hours required for the 4 machine working together to meet the order =

⇒ Total number of hours required for the 4 machine working together to meet the order =

Therefore, the total cost of machine operation to meet the order is

Total cost of machine operation = Cost of operating each machine for one hour × Total number of hours required for the 4 machine working together to meet the order

⇒ Total cost of machine operation = Rs 22.00 × 7

⇒ Total cost of machine operation = Rs 704

Hence, the answer is Option B. Rs 704.

If you think the solution is wrong then please provide your own solution below in the comments section .