hello my friends and adobe forum members...! nice to meet you , actually i am a graphic designer and my question means problem is that i received Photoshop file form customers psd format , the file size dimension is bigger like 250 feet x 12 feet for outdoor printing , but those who send this design they set normal resolution  according to them, but when i send this file to outdoor printer he said file is not good enough resolution to print on outdoor printer....now i have to make this artwork again, you can see attach artwork,  i want to know that is there is any formula or how do we know that if we are making design in Photoshop let say take this example 250 feet by 12 feet right when i open new page  i put these size 250feet x 120 feet in inches right , now my question is start from here that how i know the resolution i insert in new page  50 dpi , 20 dpi , 100 dpi .... ? how do i know what value should i insert  , to set correct pixels for printing large outdoor printer ... sorry for my english is poor

thanks in advance  for your precious time that you spend for my question... long live you and your family