A bus travels $\frac{2}{5}$ of a total journey at its usual speed. The remaining distance was covered by bus at $\frac{6}{7}$ of its usual…

A bus travels $\frac{2}{5}$ of a total journey at its usual speed. The remaining distance was covered by bus at $\frac{6}{7}$ of its usual speed. Due to slow speed it reaches its destination 50 minutes late. If the total distance is 200 kms, then what is the usual speed (in km/hr) of bus?