Calculate the number 7800

A woman came home early from work one day and found her husband in bed with a young and attractive woman.
The woman yelled at her husband in anger: “You slimy disrespectful pig! How dare you do this to me!? I’m the mother of your children, and I’ve been faithful to you all these years! I want a divorce now!”
The husband answered: “Wait a second my love, let me at least explain what happened.”
“All right, let’s hear what you have to say for yourself,” answered the wife waiting to see just how her husband would try to talk his way out of this one, “but these are your last words.”
Her husband started recalling: “today when I left work and got in my car to head home and this woman asked me for a ride.”
“I noticed that she was very skinny and wearing worn out clothes covered in muck and mud. She told me she hadn’t eaten in three days.”
“She looked worse for wear so I took pity on her and let her into the car.”
“In my mercy for her, instead of taking her straight to where she needed to go, I brought her home first and warmed her up a plate of goulash, the same plate I made for you last night which you didn’t eat claiming you’d ‘get fat’.”
“She devoured it in seconds.”
“Since she needed to get clean, I offered to let her use our shower.”
“While she showered, I noticed that her clothes were very dirty and worn, so I threw them out. She needed new clothes so I brought her the old jeans you no longer wear because they’re ‘too tight’.”
“I also gave her some underwear I bought you that you didn’t wear because ‘I don’t have good taste in clothes’.”
“I found the shirt my mom bought you for Christmas that you didn’t wear to ‘piss her off’. And I gave her the high heels you only wore once because ‘someone at work had the same pair’.”
The husband took a deep breath and continued…
“She was so grateful for my understanding and help. When I walked her to the door she turned around with tears in her eyes and asked…”
“You’re such a great person! Is there anything else your wife doesn’t use?”