A manufacturer of washing machine plans to introduce an entry-level new model to boost up his sale. the company has hired two independent market research firms MRA and MRB, to estimate the proportion of households that currently use washing machines. MRA conducted a survey of 400 households and it found 20% of the households currently using washing machines. MRB conducted a survey of 600 households and found that 18% of house holds currently use washing machines.

A)develop 95% confidence intervals for the two surveys

B)explain the reason for difference between the two surveys