Videojs with IMA sdk – Play vast pre-roll and mid-roll ad after 60 seconds

I work a lot with the video.js video player, but I’m having a problem.
Can someone help me find a solution to play a pre-roll ad and another ad at 50/60 seconds? I only find workable solutions for pre-roll. This is an example of one of the codes I work with:

var options = {
adLabel:’Anúncio’,
id: ‘my-video’,
adTagUrl:myrtag,
vastLoadTimeout:5000
};