The Sims Free Play "Get Engaged" task

[LeHoangHa]

Hi guys, I'm playing The Sims Free Play on my Lumia 525. I'm stuck at the "Get Engaged" task. It tells me to propose using the Eternity Ring, which is said to be free. But when I choose it, it tells me that I have to get more LP. So I wanna ask how many LPs is enough for this ring? Thanks for your attention.