If 50 men can do a certain job in 32 days working 8 hours per day, the part of that work which can be completed by 30 men in 64 days

If 50 men can do a certain job in 32 days working 8 hours per day, the part of that work which can be completed by 30 men in 64 days, working 4 hours per day is?

(a)  11/13

(b)  2/7

(c)  3/5

(d)  7/9

Sol:

Work done/total work=30*64*4/50*32*8=3/5