XCr,s=XBASEr,s*(1+(PRIr,s,t−1*EXRATEr−WPsWPs))elxpr1*(1+(PRIr,s,t−1*EXRATEr−WPsWPs−PRIr,s,t−2*EXRATEr,t−1−WPr,t−1WPr,t−1*𝐞𝐥𝐚𝐬𝐭𝐫𝐩𝐫s))elxpr2