Megan exercises every morning for 40 minutes. she does a combination of step aerobics, which burns about 11 calories/min and stretching which burns about 4 calories/min. her goal is to burn 335 calories during her routine.. how long should she participate in each activity in order to burn 335 calories? . a.. 20 min aerobics. 20 min stretching. c.. 22 min aerobics. 18 min stretching. b.. 30 min aerobics. 10 min stretching. d.. 25 min aerobics. 15 min stretching.