First find the difference in hourly wages: $40/hour - $30/hour = $<<40-30=10>>10/hour
Then multiply that difference by the number of hours she works in a week to find the weekly difference: $10/hour * 40 hours/week = $<<10*40=400>>400/week
Then multiply that amount by the number of weeks in a month to find the monthly difference in her earnings: $400/week * 4 weeks/month = $<<400*4=1600>>1600/month
Then find the total additional amount Janet pays in FICA taxes: $25/week * 4 weeks/month = $<<25*4=100>>100/month
Then subtract Janet's extra FICA taxes and healthcare premium from the additional money she earns to find the net increase in her pay from freelancing: $1600/month - $400/month - $100/month = $<<1600-400-100=1100>>1100/month
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