Consider this reaction:

A --> B + C

This reaction is second order. k = 0.039 M⁻¹. It required 23.0 seconds for the concentration to decrease to 0.300 M. What was the starting concentration?
a) 1.48 M
b) 9.95 x 10⁻¹ M
c) 0.410 M
d) 7.296 x 10⁻¹ M
e) 297 M
f) 3.21 x 10⁻¹ M
g) 5.81 x 10⁻¹ M
h) 8.52 M