The Chicago Tribune said it will raise the price of its daily newspaper 10 cents to 35 cents a copy in the metropolitan area beginning April 4. The first price increase since 1980 in the newspaper's primary circulation area will not affect the $1.25 cost of a Sunday paper. The paper raised its single-copy price from 20 cents to 25 cents in 1980. The price outside the metropolitan Chicago area has been 35 cents since 1982 and won't increase, the paper said. The paper blamed rising production and distribution costs, including higher newsprint prices, for the increase.