Requesting help to assess a job offer

Hello fellow expats,

Having spent a good part of the morning reading this forum / blog I can say I am whole lot more knowledgeable about accommodation / car prices (man! are cars expensive in norway) / general living costs when it comes to Norway. Thankyou all !!

Now for the reason I am posting this. I am currently working as an electrical engineer in Singapore and have been offered a position in Norway, not in Oslo, but nearby I have been scouring the internet for information but most of it seems outdated. I looked up on payscale and glassdoor with not much luck. I was hoping that I might get some help here. (Incentive: I'll buy drinks for all those who help me In norway if I decide to move or else you can have one here on a warm beech in the tropical Singapore Flight costs not included )

To my questions:
1. How much does a fresh engineering grad usually make? Any non-trivial differences between local / foreign graduates?

2. I have about 4 years of experience in electrical engineering. I understand this question is kinda broad but as a rule of a thumb is an offer of 500k NOK per annum on par with local norwegian salaries for such an experience?

3. I used the online tax calculator and I believe I would be making around 28k per month excluding the tax-deduction for foreigners for the first 2 years. Is my calculation more or less correct?

4. What exactly is holiday pay? My offer letter states 28 days of holiday pay. If I don't take all of 28 days would the rest be encashed? I have researched a lot about this and still standing at square one. Any info will be greatly appreciated.

Thanks to all in advance!!!