$1\mathrm{.}22$ The plot in Fig. P$1\mathrm{.}22$ displays the cumulative amount of charge $q(t)$ that has entered a certain device up to time $t.$ What is the current at

$($a$)t=1s$

$*($b$)t=3s$

$($c$)t=6s$

Figure P$1\mathrm{.}22$: $q(t)$ for Problem $1\mathrm{.}22.$