Two fireworks explode at the same position on the $4$th of July. A stationary observer notices that the time interval between the two events was $5\mathrm{.}00$ seconds. A second observer flies past the fireworks at a speed of $0\mathrm{.}600$ c$.$ What value does she obtain when she measures the time interval between the two explosions?

a$.$

$1\mathrm{.}67$ s

a$.$

$70$ J

b$.$

$53$ J

c$.$

$60$ J

d$.$

$64$ J

e$.$

$35$ J

$6\mathrm{.}7$ m$/$s

$1\mathrm{.}0$ Ns