I don't understand the English. I would've loved to help though.
One taco would cost about $1.20.

check your calculator for the [!] factorial button.
also bear in mind that most calculators also have an [ₙPᵣ] button, to get Permuations, and you can just use that.
Answer:
0.093 ft/min
Step-by-step explanation:
V = 4/3 π r³
Take derivative with respect to time:
dV/dt = 4π r² dr/dt
Plug in values:
141 = 4π (11)² dr/dt
dr/dt = 141 / (484π)
dr/dt ≈ 0.093
The radius is increasing at 0.093 ft/min.