Dear Sir,
After reading your job post, I deemed myself as one of the best contenders for this position.
Sir,
As a proactive and interested writer, I think I can perform your given task with my utmost sincerity and great dedication.
Sir,
I'll complete your job within your given deadline and obviously without any mistakes. Hope to work with you, Sir.
Sir,
Thanks for your time and consideration.
With Profound Regards
Sakib