81000 = 65000 + 2500*(10 – 4*ED + U_ex) + 5000*ED +  U_s(Alice) 
-> U_s(Alice) = -5000*ED - 2500*U_ex(Alice) -9000
-> U_s(Alice) = 0 - 2500*(-4) - 9000 = 1000

#Note DO NOT calculate by plug EX=6 directly:
81000 = 65000 + 2500*6 + 5000*0 +  U_s(Alice)