Heaven and her younger brother want to buy school supplies, so they ask their father for money, who gives them $100 in total to use. Heaven buys two sharpeners and four notebooks at $5 each, and her brother uses the remaining amount to buy ten erasers at $4 each and some highlighters. How much money did Heaven's brother spend on highlighters?
Heaven spent 2*5=$<<2*5=10>>10 on sharpeners.
She also spent 4*5 = $<<4*5=20>>20 on notebooks.
Heaven's brother used 10*4 = $<<10*4=40>>40 to buy erasers.
The total amount of money Heaven and her sister spent on sharpeners, notebooks, and erasers is 40+20+10 = $<<40+20+10=70>>70
The total amount of money her brother spent on highlighters is 100-70 =$<<100-70=30>>30
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