During the Covid$-19$ pandemic, Harry's shoes, a local handmade shoe shop, struggled to get raw materials and pay his rent. After the pandemic, all his costs increased astronomically. At this stage Harry needs to decide if he can afford to keep his shoe shop open.

Currently Harry's costs are R$300$ per pair of shoes, what would the selling price per pair of shoes be to maintain a $50\%$ mark$-$up$?$

R$150$

$R600$

$R450$

R$350$