Help finding Model number and Serial number on laptop

Basically, my warranty is with another company called "WarranTech" and they need the model number and serial number of the laptop. Only issue is that my laptop motherboard has been fried, i've tried installing new RAM and even went to a repair shop and they told me that to fix the motherboard it'd be more than the laptop is worth. Also, I've had the laptop for quite a while and on the bottom where the SN/MN is printed the label is very faded. I took it to Geek Squad at Best Buy and they tried using a magnifying glass to identify it, and did not succeed. So essentially my problem is that I can't use the warranty I paid 75$ for without paying atleast 200$ to install a new motherboard. This laptop is rented so even though I cant use it I still have to pay for it until my credit to the rental company is paid, they kept no records of the MN/SN, nor the purchase of the laptop. Am I screwed? Or is there some way to either externally find the MN/SN or some way I can provide one of the codes behind the battery to link it to the MN/SN? Thanks in advance. 

PC info - Dell Inspiron 15-3521 1.90GHz Pentium 2127u.

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