Why don’t the company’s costs increase proportionately as the revenues increase in the third and fourth quarters?

The Company has experienced a pattern of business whereby revenue for its third and fourth fiscal quarters reflects an increase over first- and second-quarter revenue. The Company attributes this increase to clients’ increased spending at the end of their calendar year budgetary periods and the culmination of its annual sales plan. Since the Company’s costs do not increase proportionately with the third- and fourth-quarters’ increase in revenue, the higher revenue in these quarters results in greater profit margins and income. Fourth-quarter profitability is traditionally affected by significant new hirings, training, and education expenditures for the succeeding year.

Also another question is :

What type of budgeting seems appropriate for the Computer Associates situation?