What size of sheet of coroplast do i need to get for this c&c cage?

http://www.google.com/imgres?imgurl=http://www.guineapigcorner.com/images/c-and-c-cage.jpg&imgrefurl=http://www.guineapigcorner.com/cages&usg=__4SncpMauzwsTYW4PnTb7ZzHLhMg=&h=300&w=400&sz=22&hl=en&start=0&sig2=OKGP7-i3eJvCTQoC7yAGxQ&zoom=1&tbnid=8We_o5Tv8esqwM:&tbnh=137&tbnw=162&ei=bu7STZTxL6bk0gH2y9zOCw&prev=/search%3Fq%3Dc%2526c%2Bcages%2Bfor%2Bguinea%2Bpigs%26hl%3Den%26sa%3DX%26rlz%3D1R2ADFA_enUS412%26biw%3D1007%26bih%3D577%26tbm%3Disch%26prmd%3Divns&itbs=1&iact=rc&dur=703&sqi=2&page=1&ndsp=13&ved=1t:429,r:11,s:0&tx=88&ty=73