When their favorite restaurant charged $30 per meal (per person), Mr and Mrs Bell dined out once a week. Ceteris paribus, when the restaurant, as the promotional gimmick, introduced a voucher system giving patrons two meals for the price of one, Mr and Mrs Bell dined out three times a week at the restaurant.

a. Calculate the couple's elasticity of demand for restaurant meals. Measure quantity demanded in terms of number of meals bought each week.

b. What happened to their weekly expenditure on restaurant meals as the effective price per meal fell? Is the change in total expenditure consistent with the value of elasticity of demand you calculated?