Please show calculation process (not excel)

Amelia has a monthly net income of RM 640. Her fixed monthly expense consists of a room rent payment of RM120. She also has a secondhand car payment of RM125 per month. Amelia wants to buy secondhand tires for her car. The secondhand tires will cost her RM40 each month on his credit card.

a. Right now, calculate how much can Amelia afford to borrow to stay within his safe debt load.

b. With Amelia car payment and the new tires. Calculate either she is still in a safe debt load or otherwise. Justify your answer.