How many kilograms are there in 9.28e-5 ng.?

Question

Answer example 2.72e-3

Answer 1

Is it really e-5?

If so e = 2.71828183, and 9.28e^-5ng=0.0625ng.

kg=0.0625ng/(10^12ng/kg) = 6.25 x 10^-14 kg

Must be some missing mathematical notations, if 2.72e-3 is correct.

Also base e and base 10 exponents can NOT be added without changing one or the other to have the same base.

Answer 2

1 ng = 1×10^-9 g, and 1 g = 1×10^-3 kg, so 1 ng = 1×10^-12 kg

9.28e-5 ng = 9.28e-17 kg