What solder specs are safe to use when soldering wires to an Mk2a heat bed? I've already asked which wires I should use, and I believe I have that covered now, but I was also wondering what solder / specs on the solder are considered safe when attaching my wires to my heat bed.  I have some solder here at the house, it's quite new (never been opened) it's Radio Shack 64-008 E 60/40 Standard Rosin-Core with 0.062 diameter...
Old-style lead/tin solder has a melting range of about 180 to 250 degrees (the transition solid to liquid is spread out). This ought to be fine for the bed (even at the hottest hotspot) but wouldn't be good in the hotend.

Modern electronics lead-free solder varies since there are several different compositions, but is typically a bit higher in melting point (by some 10s of degrees).

Special high melting point solder transitions around 300C, but you would only need to use this in very specific scenarios.