#### In the first month after opening, a mobile phone shop sold 280 phones. A model for future trading assumes that sales will increase by x phones per month for the next 35 months,

so that (280 + x) phones will be sold in the second month, (280 + 2x) in the third month, and so on. Using this model with x = 5,

Calculate, the total number of phones sold over the 36 months.