$.$ The National Ignition Facility $($NIF$),$ which became operational in $2009,$ uses $192$ laser beams

to stimulate nuclear fusion in a deuterium$-$tritium fuel pellet. The net output of the lasers is $1\mathrm{.}8$

MJ of $351-$nm light, delivered in a brief $(4\mathrm{.}0-$ns$)$ pulse. $($a$)$ What is the average power

delivered during the pulse? Compare your answer with the average power consumption in

the United States, about $3$ x $10$

$12$ W$.($b$)$ How many photons are produced in each pulse?