hi could you pls explain how to do these two in detail? thanks!

14. A neutron leaves an accelerator at Brookhaven every 6 nanoseconds. To an observer flying overhead with a velocity of 0.8 c relative to the earth in the direction of the neutron's motion the neutrons appear to be leaving at intervals of

(a) 4 ns(b) 8 ns(c) 10 ns(d) 12 ns

15. An observer on earth measures the velocity with which the neutrons leave. She gets 0.8c.

How fast does the observer above the earth moving at 0.8 c relative to the earth think the neutrons are moving?

(a) 0.98 c(b) 0.67 c(c) 0.77 c(d) 0.89 c