Allí va tu respuesta, saludos :
<img src="https://tex.z-dn.net/?f=5%2A100W%2A6h%3D%203%20000W.h%3D%203KW.h" />
<img src="https://tex.z-dn.net/?f=1%2A180W%2A3h%3D540W.h%3D%200%2C54KW.h" />
<img src="https://tex.z-dn.net/?f=1%2A600W%2A1h%3D600W.h%3D0%2C6KW.h" />
sumamos ;
<img src="https://tex.z-dn.net/?f=%283%2B0%2C54%2B0%2C6%29KW.h%3D4%2C14KW.h" />
Costo de la energía durante el día ;
<img src="https://tex.z-dn.net/?f=4%2C14%2Acosto%20del%20kw.h" />
<img src="https://tex.z-dn.net/?f=4%2C14%20KW.h%2A1%20%2A0%2C25%20centavos%20de%20dolar%2F%20KW.h%3D%20%24%201%2C035%20d%C3%B3lares%20americanos" />
Costo de la energía para un mes ;
<img src="https://tex.z-dn.net/?f=4%2C14%20KW.h%2A30%2A0.25%20cent%2F%20KW.h%3D%24%2031%2C05%20dolares%20americanos" />.