A can do $$\frac{4}{5}$$ of a work in 20 days and B can do $$\frac{3}{4}$$ of the same work in 15 days. They work together for 10 days. C alone completes the remaining work in 1 day. B and C together can complete $$\frac{3}{4}$$ of the same work in:

Let total work to be done be 20 units

A can do 16 units in 20 days, => A's efficiency = $$\frac{16}{20}=0.8$$ units/day

Similarly, B can do 15 units in 15 days, => B's efficiency = $$1$$ unit/day

Now, work done by A and B in 10 days = $$(1+0.8)\times10=18$$ units

Also, remaining work i.e., 2 units is completed by C in 1 day, => C's efficiency = $$2$$ units/day

$$\therefore$$ B and C can complete $$\frac{3}{4}$$ of the same work i.e., 15 units in = $$\frac{15}{2+1}=5$$ days

=> Ans - (B)