Is the current strategy for many manufacturers where a company produces a large quantity of items but customizes them to match the needs and preferences of individual customers.

Business khalid charges $10 for a one-year subscription to his on-line newsletter. khalid currently has 600 subscribers and he estimates that for each $1 decrease in the subscription price, he would gain 100 new subscribers. what subscription price will maximize khalid's income? if he charges this price, how much income should khalid expect?