Each week she makes $20 * 40 = $<<20*40=800>>800 from her normal hours.
For overtime she makes $20 * 1.5 = $<<20*1.5=30>>30 per hour.
Each week she works 52 - 40 = <<52-40=12>>12 overtime hours per week.
She makes a total of 12 * $30 = $<<12*30=360>>360 from overtime every week.
This means she makes a total of $800 + $360 = $<<800+360=1160>>1160 per week.
To reach $4640 she would need to work $4640 / $1160 = <<4640/1160=4>>4 weeks.
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