A car moving along a straight line covers 1/5 th of total distance with speed v₁ and remaining part of distance with speed v₂ . The average speed of the car over entire distance is:

a. v₁ + v₂/2
b. 2v₁v₂/v₁ + v₂
c. 2v₁v₂/3v₁ + 2v₂
d. 3v₁ + 2v₂/5