Question

PLEASE HELPPP. WILL MEDAL!!!!
Determine the radius and circumference of the circle containing all points at latitude 45 degrees, given that the radius of the Earth is approximately 4000 miles. If Belgrade's and Wakkanai's latitude is 45 degrees, Belgrade's longitude is approximately 20 degrees E and Wakkanai's is 140 degrees E, (you have 120 degree difference between the longitudes) find the distance between the two cities, if one travels along the 45 degree latitude.