Konnor wants to burn 250 calories while exercising for 45 minutes at the gym. on the treadmill, he can burn 6 cal/min. on the stationary bike, he can burn 5 cal/min. if t represents the number of minutes on the treadmill and b represents the number of minutes on the stationary bike, which expression represents the number of calories that konnor can burn on the stationary bike?