An electron in a cathode$-$ray$-$tube $($CRT$)$ accelerates uniformly from $9\mathrm{.}00{10}^4\frac{m}{s}$ to $6\mathrm{.}00{10}^6\frac{m}{s}$ over $1\mathrm{.}50cm.$

$($a$)$ In what time interval does the electron travel this $1\mathrm{.}50cm?$

s

$($b$)$ What is its acceleration?

$\frac{m}{s^2}$

$($Just a number should be the answer$)$