Correct Answer - 1024
Let a be the first term and r be the common ratio of the GP. Then, the first five terms are `a, ar, ar^(2), ar^(3), ar^(4)`.
Also, `T_(3)=4 rArr ar^(2) =4`.
Product of first five terms `=(axxarxxar^(2)xxar^(3)xxar^(4))=a^(5)r^(10)=(ar^(2))^(5)=(4)^(5)=1024`.