Dr$.$ John Paul Stapp was a U$.$S$.$ Air Force officer who studied the effects of extreme deceleration on the human body. On December $10,1954,$ Stapp rode a rocket sled, accelerating from rest to a top speed of $282$ m$/$s $(1015$ km$/$h$)$ in $5\mathrm{.}00$ s$,$ and was brought jarringly back to rest in only $1\mathrm{.}40$ s$!$ Part $($a$)$ Calculate the magnitude of his average acceleration during the first part of his motion. Express your answer in multiples of g by taking its ratio to $9\mathrm{.}80$ m$/$s$2.$Part $($b$)$ Calculate the magnitude his average deceleration during the second part of his motion. Express your answer in multiples of g by taking its ratio to $9\mathrm{.}80$ m$/$s$2.$