Mr. Robert's budget for phone fee, utility and rent was $1200 per month. He spends 17% of it on phone feet, 28% of it on utility and the remaining for rent. The rent was fixed for each month. If he wants to decrease his budget for utility by 10% the following month,
(a) How much can he spend on phone fee with the same amount of budget?
(b) What’s the spending difference of his phone after his changing?