Video editing for a lecture

I have this job. specification as below. My budget is about £100.

- video is of a lecture, recorded using a HD 1080p webcam with a poor sound quality
- audio file is recorded using a mobile phone and produced good sound quality.

Need to
- merge the video and audio file together
- enhance the sound quality of the audio file because the primary speaker is very loud but the audience is somewhat softer (like in the background).

lecture duration is about 95min.
no special effects/enhancement required for video editing.
output file to be optimized for web use

Need it by next Monday.