Problem $14$: A floating$-$point operation is a single arithmetic operation such as addition, subtraction, or division.

Estimate the maximum number of floating$-$point operations a human being could possibly perform in a lifetime. That is$,$ how many of these calculations could they do $*$in their own head$*$ during a lifetime, while still sleeping and doing other tasks that might prohibit them from doing such calculations in their head? Clearly explain all estimates.