Physics Current Electricity Level: Misc Level

In the figure  R1 =81 Q, R2=67 Q, and the ideal batteries have emfs E1 =8.0 V, E2 =5.0 V, and E3 =4.0 V. Find (a) the current in R1, (b) the current in R2, and (c) the potential difference between points a and b.