assuming that all the bees do an equal amount of work in an equal time span.

(a) 40 bees finish 1 work in 30 hours.

=> (b) 40 bees will finish 1/30 work in 1 hour.

=> (c) 1 bee will finish 1/1200 work in 1 hour.

=> (d) 1 bee will finish 1 work alone in 1200 hours.

**considering statement (b): **

40 bees will finish (10/30=)1/3 work in 10 hours.

remaining work to be done= 1-1/3 = 2/3 work, and

remaining number of bees= 40-15 = 25 bees

Now, 25 bees have to do the remaining (2/3)^{rd} work.

**considering statement (d): **

25 bees will finish 1 work in = 1200/25 hours.

So, 25 bees will finish remaining (2/3)^{rd} work in = (1200/25) * (2/3) = 32 hours