Toggle 3 pins PC0, PC1 and PC2 corresponding to INT0, INT1 and Timer0 respectively. Whenever any of the interrupts occurs, the corresponding pin should toggle. Configure Timer 0 to generate the longest possible delay, whenever the overflow occurs, toggle the pin corresponding to it. In the proteus, you need to use three LEDs to PC0, PC1 and PC2,PC0 and PC1 should toggle whenever the buttons connected to INT0 and INT1 are pressed. PC2, on the other hand, should toggle whenever Timer0 overflows.