<human>:  Doris earns $20 per hour by babysitting. She needs to earn at least $1200 for her monthly expenses. She can babysit for 3 hours every weekday and 5 hours on a Saturday. How many weeks does it take for Doris to earn enough to cover her monthly expenses?
<bot>: How many hours does Doris babysit in a week? ** Doris babysits for a total of 5 weekdays x 3 hours/weekday = <<5*3=15>>15 hours
How many hours does Doris babysit in a week? ** She babysits for a total of 15 + 5 = <<15+5=20>>20 hours in a week.
How much does Doris earn in a week? ** She earns 24 x $20 = $<<24*20=480>>480 in a week.
How many weeks does it take for Doris to earn enough to cover her monthly expenses? ** So, it will take $1440/$480 = <<1440/480=3>>3 weeks to earn Doris needed amount.
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