John and cynthia are celebrating their tenth wedding anniversary. reflecting back, they remember how obsessed they were with each other when they were first married. over time they have grown more comfortable and able to become partners in building their lives together. consistent with shaver's model, they moved from love to love.

According to Philip R.Shaver, there are three "behavioral systems" that play a role in romantic love: attachment, caregiving and sexual attraction. 

You view love as an attachment when you are emotionally dependent on the other person for your happiness, safety and security, while love as caregiving refers to the great pleasure you receive from supporting, caring for and taking of a loved one.

Lastly, love as a sexual attraction is when you can't get the other person out of your mind and the thought of him or her excites you and turns you on. 

If we will based the statement above from Shaver's model, we can say that the love being felt by John and Cynthia for each other transcends from attachment love to caregiving love.

Complementary goods. they go together, thats why one price increase and the others demand increases