Waiting period. Jamal is waiting to be a millionaire. He wants to know how long he must wait if

a$.$ he invests $$23,520\mathrm{.}19$ at $22\%$ today?

b$.$ he invests $$48,865\mathrm{.}91$ at $15\%$ today?

c$.$ he invests $$158,671\mathrm{.}18$ at $8\%$ today?

d$.$ he invests $$311,041,69$ at $6\%$ today?

a$.$ How long will Jamal have to wait to become a millionaire if he invests $$23,520\mathrm{.}19$ at $22\%$ today?

$$ years $($Round to the nearest whole number.$)$