A sales consultant for Herron Pharmaceuticals wished to confirm that their packet of 24 paracetamol tablets was cheaper at the retail level than...

A sales consultant for Herron Pharmaceuticals wished to confirm that their packet of 24 paracetamol tablets was cheaper at the retail level than their rival product. The sales consultant collected price data from two independent samples, of size 19 for Herron and 26 for the rival company. These yielded an average and variance for the retail price of Herron's product of 326 cents and 55 cents squared respectively, and 384 cents and 67 cents squared for the rival. Under the usual assumptions, determine an 80% confidence interval for the price difference (use Herron minus rival) stating only the lower limit of the interval in cents (round to the nearest whole number).