Question

When a satellite is h kilometres above Earth,the time,t,in minutes,to complete one orbit is given by the formula t=Root of (6370+h)^3/6024

a) A telecommunications satellite is placed 30 km above Earth. How long does it take the satellite to make one orbit?

b) A satellite is placed in geosynchronous orbit about Earth. What must its altitude be?

*the satellite is travelling at more than 11,000 km/h
Please help me understand this. Thank you!!