If he sold a painting at a 10% loss, then he made a 10/100*$40 = $<<10/100*40=4>>4 loss on each painting.
since he bought 10 paintings, the total loss he made from selling the paintings is 10*$4 = $<<10*4=40>>40
He also made a loss of 15/100*20 = $<<15/100*20=3>>3 loss from selling each wooden toy.
Since he bought 8 wooden toys, the total loss he made was 3*8 = $<<8*3=24>>24
In total, Mr. Callen made a loss of $40+$24 = $<<40+24=64>>64 from the sales of the items.
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