yesterday I purchased (secondhand) Lingua Latina by Oerberg

I'm currently studying Latin using Henle and I need a break. Due to the enthousiasm here for LL, I decided to try it.
Today I realised that I have no way of grading the pensa, as I do not have the answers and the introductory booklet advises me to send my pensa to the teachers associated with the publisher of the books ...... yeah, in 1965.

Do any of you know of a way to solve this problem? A website or something, of someone who has used this version?? Or should I just admit that I made a costly mistake

regards,
Miriam