A rice company decides to combine a firstrate rice that costs 5000 per kilo with a secondrate type that costs 4000 per kilo. The result is a new type of rice which costs 4600 per kilo. How many kilograms of the first rate rice are there in 40 kilo of the new type of rice?

A.24

B.32

C.30

D.33

Please explain the solution clearly.With many thanks.