Dear Hiring Manager,
This is a research paper implementation project and requires the work to be done with full attention and responsibility. Moreover, it is not possible to do it in less than 20 days. I have worked on 2 research paper, and I know how much hard work is required for these.
That is why it is impossible to complete in less than 500 SGD, if you award it to someone at lesser price and he ensures you he will complete in 15 or even 20 days, I recommend you not to trust on him.
This is the sure thing, and a free advice!! You might try it, and tell after you waste your time and money on him.
I advised the same to someone else almost 2 weeks ago. I bid on his project at $400, but he awarded the project at $120. After 3 days he re-posted the same project at $177 to another person, and after 3 days started messaging me to do! But unfortunately I couldn't contact him (BECAUSE once the project is awarded to a freelancer, the other freelancers can't send the message to client, the same happened with us: he sent me messages but I couldn't reply him).
Thanks.