Thank you for the opportunity to help you with your question!

50 calories are consumed per mile

for 15 miles per hour, calories consumed= 50*15=750 calories per hr, this is equal to 750/3600= 0.2083 calories/second, given that, 1 calorie per sec=4.19 watt, the average power output= 0.2083*4.19= 0.873 Watts

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