newbie, help with datasheet equation

[inevitski]

Hi,

I have a question regarding equation I found in a datasheet.
I have a problem calculating junction temperature in an
IC from linear tech, model number: LT3761

the datasheet link: http://cds.linear.com/docs/en/datasheet/3761f.pdf

The equation is: TJ = TA + [VIN (IQ + fSW • QG) • ?JA] 

The practical example is:
 TJ = 85°C + [40V • (2mA + 400kHz • 20nC) • 43°C/W]

The sollution offered in the schematic is TJ = 102°C, but I can't figure out how they came up with it,
I am still young and very new to this, and would be very gratefull if someone on this forum has the
patience to show how I can solve it properly or point me in the right direction.

Thank you,
inevitski

[Rerouter]

Take note of the engineering units 85 + (0.002 + 400000 * 0.00000002) * 40 * 43

it comes to 102.2

[inevitski]

Thank you rerouter!
 

inevitski