$(10$ points$)$ The current density in a cylindrical wire is given as $5\mathrm{.}89{10}^6\frac{A}{m^2}.$ Find the current in the wire if its diameter is $1\mathrm{.}80$ mm $.$

Answer: $14\mathrm{.}99A$~~$15A$

$2.(10$ points$)$ A rectangular block of a conductor, whose resistivity is $1\mathrm{.}74{10}^{-8}.$m$,$ has dimensions $aab$ as shown in the figure. If $a=3cm$ and resistance of the conductor is $R=2\mathrm{.}9{10}^{-6},$ what is the value of $b?$

Answer: $0\mathrm{.}15$ m

$3.(10$ points$)$ What is the resistance of a toaster if $120$ V produces a current of $4\mathrm{.}2$ A $?$

Answer: $28\mathrm{.}57$