"He bought his first oil refinery in 1862, and by 1870 set up Standard Oil Company of Ohio, made secret agreements with railroads to ship his oil with them if they gave him rebates - discounts - on their prices, and thus drove competitors out of business
a. These agreements were secret so that competitors would also sign up for rebates
b. These agreements were secret so that other businesses wouldn't know that Standard Oil was paying lower prices
c. Competitors didn't care about these secret agreements"