Mall A: Send it to 25 yuan when it is over 100 yuan, and you can use 250 yuan for shopping. Send it to 50 yuan when you are in 200 yuan, and your total shopping amount can reach 300 yuan.

Mall C: 15% discount. When you shop in 250 yuan, the amount before discount is 250/0.85 = 294.38+02 yuan.

So it's cost-effective to go shopping in mall A.