A fashion company spends $10 to produce a pair of jeans and $2 to produce a shirt. During a typical month, they spend $3500 on the production of jeans and shirts. During months in autumn, though, they double the pairs of jeans produced and spend a total of $6000. How many pairs of jeans and t-shirts does the company make during a typical month? Let j = number of pairs of jeans and k = number of shirts.