P and Q are two points on latitude 55°N and their longitudes are 33°W and 20°E respectively. Calculate the distance between P and Q measured along (a) the p...

P and Q are two points on latitude 55°N and their longitudes are 33°W and 20°E respectively. Calculate the distance between P and Q measured along 

(a) the parallel of latitude ;

(b) a great circle. 

[Take \(\pi = \frac{22}{7}\) and radius of the earth = 6400km].